A scientist who has spent much of his career studying paralytic shellfish poisoning has an all-encompassing theory about what may have killed gobs of threatened and endangered marine mammal predators in Alaska, not to mention the vaunted king salmon that appears to be on the decline in some of the state's waterways.

The hypothesis involves the tiny sand lance, a pencil-shaped fish found along Alaska's coasts that gets gobbled up by animals seeking a fatty burst of energy, including Steller sea lions, sea otters and northern fur seals, species of concern that have seen stunning population drops in Western Alaska.

Also chowing down on the fatty forage fish, which takes shelter in the sand up and down Alaska's coasts, are salmon and birds, said Bruce Wright, a senior scientist with the Aleutian Pribilof Islands Association, which provides social services to tribal communities in the Aleutians region.

"They're a super important part of the ecosystem out there," said Wright, 61, who started in Alaska in 1978 working for Fish and Game and sampling for PSP at the commercial geoduck fishery in Ketchikan.

If Wright's theory is correct, the sand lance might also have caused some big problems in the region as the climate has warmed. Sand lance eat tiny organisms contaminated by the toxins associated with paralytic shellfish poisoning. And those toxins, as humans know, move up the food chain.

When most Alaskans think of paralytic shellfish poisoning, they think of mussels and clams and state alerts warning subsistence users of potential sickness or death when shellfish have high levels of the toxins. PSP in humans has been an increasing problem: Since 1973, the state has experienced a sevenfold increase in such outbreaks, said Wright, citing information from the state Department of Epidemiology.

The idea that sand lance might also be harboring high levels of PSP toxins is new to her, said Catie Bursch, a state Fish and Game employee from Homer who works with volunteers to monitor Kachemak Bay for PSP, where levels are typically low.

"Most of the time we have thought of PSP as a problem with animals living on the bottom of the oceans that filter feed," Burcsch said. "It hasn't been documented as much going up the food chain."

Filter feeders such as clams ingest a tiny phytoplankton called alexandrium that can harbor the toxins. Sand lance ingest the toxins in a more roundabout way, after eating zooplankton that eat the alexandrium.

Outbreaks of paralytic shellfish poisoning seem to reach across more of the state than they once did, and to occur more often in winter, said Wright.

Climate change may be a factor in the growth of PSP, with more winter rains creating more opportunity for the creation of algal blooms as freshwater runoff spills into the sea. When the freshwater nutrients sit atop saltwater without being disturbed by, say, strong winds, the area where the two waters meet can form the perfect nursery for the toxic organisms, Wright said.

Those toxins have been found in sand lance and the animals that eat them, he said. In 2012, several Kittlitz's murrelets on Kodiak Island were found dead after eating PSP-contaminated sand lance, Wright said. The combination also led to a die-off of terns in 1978 on the East Coast, Wright said.

Wright, who has annually monitored PSP in clams and mussels in the Aleutians since 2006, said it's possible that PSP-contaminated sand lance could have caused huge drops in populations of threatened fur seals and sea otters, as well as endangered Steller sea lions, if they'd eaten large batches of contaminated fish.

He even suggests that a lot of juvenile king salmon could have been wiped out after eating contaminated sand lance along the remote and barely populated Aleutian Islands, where large numbers of salmon could disappear and never be noticed, he said.

"You can take out a whole year class of king salmon and everyone would blame it on bycatch," Wright said, referring to the accidental take of king salmon by the pollock trawlers. "Bycatch is certainly an issue, but sand lance could be too."

Wright recently won funding from the Environmental Protection Agency to study PSP in sand lance. Part of the project will involve working with local technicians in communities along the Alaska Peninsula and Aleutian Islands.

Those technicians already scout for PSP in clams and mussels at 10 sites in the Aleutian and Pribilof islands. If levels of toxins spike in those locations, such as in Unalaska, Wright said he'll travel to the area to capture the sand lance so they can be tested as well.

With help from local observers, he'll also be looking for birds or animals that may have died after ingesting toxic sand lance, so the animals can be tested for paralytic shellfish poisoning as well.

"If PSP is a big player, we should have a discussion about that, and not just about the bycatch and other problems that might be causing these declines," he said.